(1) Field of the Invention
This invention relates to the treatment of an intermetal dielectric layer to stabilize the dielectric constant of the intermetal dielectric. More specifically the invention relates to the treating of an intermetal dielectric layer in an inert atmosphere at elevated temperature.
(2) Description of the Related Art
In integrated circuit wafers is common to have a structure of a patterned layer of conductor material, a first silicon oxide layer deposited on the conductor material, an intermetal dielectric layer deposited on the first silicon oxide layer, and a second silicon oxide layer deposited on the intermetal dielectric layer. A patterned layer of second conductor material is then formed on the second silicon oxide layer. One of the problems of this structure is that the steps of depositing the second silicon oxide layer and alloying the second conductor material degrades, or increases, the dielectric constant of the intermetal dielectric layer. This increase in dielectric constant results in increase of stray capacitance which is very undesirable. This invention describes an inert atmosphere treatment of the intermetal dielectric layer in order to prevent this degradation of dielectric constant from occurring.
U.S. Pat. No. 5,643,407 to Chang describes a nitrogen plasma treatment of the exposed edge of a spin-on-glass layer after etching a via hole to prevent via hole etching.
U.S. Pat. No. 5,270,267 to Ouellet describes a method of precuring a film of spin-on-glass to remove the bulk of the solvents followed by curing of the film in a plasma reactor to remove the bulk of the SiOH, organic volitles, and H.sub.2 O form the film.
U.S. Pat. No. 5,567,658 to Wang et al. describes a method of removing polymeric deposits from the surface of a spin-on-glass layer to prevent peeling of subsequently formed layers of material. The method describes exposing the surface of an etched back spin-on-glass layer to a gas discharge plasma of nitrous oxide or nitrogen.
U.S. Pat. No. 5,393,702 to Yang et al. describes a structure which includes an intermetal dielectric layer of spin-on-glass. A via hole is etched in the intermetal dielectric layer. A silicon nitride cap is then formed on the exposed edges of the spin-on-glass intermetal dielectric layer to prevent outgassing of the spin-on-glass and subsequent via poisoning.